JP5217236B2 - Fuel cell catalyst containing RuTe2 and N element, fuel cell electrode material and fuel cell using the fuel cell catalyst - Google Patents

Description

The present invention relates to a fuel cell catalyst containing RuTe ₂ and an N element, a fuel cell electrode material using the fuel cell catalyst, and a fuel cell.
The present invention also relates to a fuel cell stack and a fuel cell system using the fuel cell.

  In recent years, in order to further improve energy efficiency and solve environmental problems, attempts have been made to clean exhaust gas by using a fuel cell as a power source for automobiles. ing. In particular, development of a polymer electrolyte fuel cell (PEFC) as a fuel cell for a fuel vehicle (FCHV) has been rapidly progressing.

  A fuel cell is a power generator that supplies fuel to the anode and oxidant to the cathode, takes out the potential difference between the anode and cathode as voltage, and supplies it to the load. Hydrogen is commonly used as the anode fuel, and oxidant is generally used as the oxidant. For this, oxygen in the air is used. A fuel cell is composed of an anode and a cathode and an electrolyte sandwiched between them. In a polymer electrolyte fuel cell, an ion exchange membrane is used as an electrolyte. Specifically, an electrolyte membrane / electrode assembly in which a catalyst layer is formed on both surfaces of an ion exchange membrane as an electrolyte, and an anode gas diffusion layer and a cathode gas diffusion layer are integrally formed on the outside of the catalyst layer, respectively. A unit cell composed of a barrier plate, an electrolyte membrane / electrode assembly, and a barrier plate laminate is formed by stacking several tens to several hundreds of cells so as to obtain a desired voltage according to the application. Yes.

  In such a fuel cell, when hydrogen reaches the anode catalyst layer, protons and electrons are generated by an electrochemical reaction process. Protons generated here move sequentially in the electrolyte and reach the cathode. On the other hand, electrons are sent to the cathode via an external load. In the cathode catalyst layer, electrons sent via an external load, oxygen in the air as an oxidant, and protons that have moved through the electrolyte combine to form water through an electrochemical reaction process. .

  Conventionally, as a catalyst for such a fuel cell, a catalyst based on a noble metal such as platinum, which is expensive and has a problem in terms of resources, has been used for both the cathode and the anode. The amount of platinum used for the exhaust gas purification catalyst of gasoline cars is considerably larger than that of platinum.

  Therefore, in order to commercialize fuel cells, development of fuel cell catalysts that can be put into practical use at low cost, replacing catalysts based on precious metals such as platinum, which are problematic in terms of price and resources. Is one of the essential issues.

Non-Patent Document 1 discloses a RuNx / carbon black catalyst in which Ru as an active component is treated with urea and supported on carbon black. In this non-patent document 1, the effects of NH ₃ and urea, which are basic organic compounds, are examined, and the effect of improving the oxygen reduction reaction activity by adding urea is obtained, but there is almost no effect of adding NH ₃ , It has been shown that the introduction of a nitrogen atom into the Ru element does not necessarily improve the oxygen reduction reaction activity. In addition, only basic organic compounds such as NH ₃ are disclosed as nitrogen source compounds, and there is no disclosure or suggestion of acidic inorganic nitrogen-containing compounds such as nitric acid. Of course, the central element of the active component in Non-Patent Document 1 is only Ru, and there is no disclosure of RuTe ₂ .

Non-Patent Document 2 discloses a catalyst obtained by treating a Ru / C catalyst with Fe (1,10-phenanthroline) ₃ and NH ₃ . Non-Patent Document 3 discloses a RuNx / C catalyst and a RuFeNx / C catalyst. However, in both cases, the central metal of the active component is only the Ru element, and RuTe ₂ is not disclosed at all. In addition, since the mechanism for improving the oxygen reduction reaction has not been elucidated, the effect of adding N element and Fe element to RuTe ₂ is not suggested.

On the other hand, Patent Document 1 discloses a RuTe ₂ catalyst deposited on a carbon-based substrate or the like, and a transition metal may be further deposited on the substrate, and Fe element is exemplified as the transition metal. However, in this Patent Document 1, it is only disclosed as an invention that the activity is remarkably improved when the Te / Ru ratio of the produced catalyst exceeds a predetermined value, and other elements such as Fe element are disclosed. The catalyst component may only be further applied to the substrate as long as the effects of the present invention are not impaired. Of course, this Patent Document 1 does not describe the N element, and does not suggest any improvement in the oxygen reduction reaction start potential (Onset Potential) by combining the N element with RuTe ₂ .
WO2006 / 137302 Journal of The Electrochemical Society 154 (2) (2007) A123 Lingyum Liu et al. Journal of Electroanalytical Chemistry 578 (2005) 339 M. Bron et al. Journal of Power Sources 162 (2006) 1099 Lingyun Liu et al.

  As described in Patent Document 1, it is known that an alloy of ruthenium and tellurium can be used as a fuel cell catalyst. However, this fuel cell catalyst has a high cathode activity at about 0.5 V or less (base). However, since the oxygen reduction reaction starting potential is low, there is a difficulty as a fuel cell catalyst that can give a high potential, and it was necessary to improve the oxygen reduction reaction starting potential for practical use.

Therefore, the present invention is a RuTe ₂ fuel cell catalyst that exhibits an excellent catalytic action that is inexpensive and can be substituted for a noble metal catalyst such as platinum, and has a high oxygen reduction reaction initiation potential, An object of the present invention is to provide a fuel cell electrode material, a fuel cell, a fuel cell stack, and a fuel cell system using the fuel cell catalyst.

As a result of intensive investigations in view of the above circumstances, the present inventors have found that RuTe ₂ which is an inexpensive catalyst for fuel cells that can be replaced with a noble metal catalyst such as platinum is N element, or further It has been found that by adding Fe element, the oxygen reduction reaction start potential is increased, and a fuel cell catalyst that gives a large current at a higher potential can be obtained.
The present invention has been completed based on such knowledge, and the gist thereof is as follows.

[ 1 ] A catalyst for a fuel cell comprising RuTe ₂ as an active component, wherein the active component is deposited on a carbon-based substrate that has been heat-treated with a compound containing an N element.

[ 2 ] The fuel cell catalyst according to [ 1 ], wherein the carbon-based substrate is further heat-treated with a compound containing Fe element.

[ 3 ] An electrode material for a fuel cell comprising an ion exchange membrane and a layer of the catalyst for a fuel cell according to [1] or [ 2] formed on the ion exchange membrane.

[ 4 ] An electrode material for a fuel cell, comprising: an electrode gas diffusion layer; and a fuel cell catalyst layer according to [1] or [ 2] formed on the electrode gas diffusion layer.

[ 5 ] A fuel cell electrode material comprising: a transfer film; and the fuel cell catalyst layer according to [1] or [ 2] formed on the transfer film.

[ 6 ] A fuel cell using the fuel cell catalyst according to [1] or [ 2] .

[ 7 ] A fuel cell stack using the fuel cell according to [ 6 ].

[ 8 ] A fuel cell system using the fuel cell stack according to [ 7 ].

According to the present invention, it is an inexpensive and practical fuel cell that shows a good catalytic action that can be replaced with an expensive and resource-problem noble metal catalyst such as platinum, and has an increased oxygen reduction reaction starting potential. Provided are a catalyst, a fuel cell electrode material, a fuel cell, a fuel cell stack, and a fuel cell system using the fuel cell catalyst.
According to the present invention, since a practical fuel cell is provided by an inexpensive fuel cell catalyst excellent in applied voltage durability, the application of the fuel cell to a fuel vehicle, a fixed cogeneration system, etc. Practical use is promoted.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[Fuel cell catalyst]
The fuel cell catalyst of the present invention contains RuTe ₂ and N element or further Fe element as active components.
The fuel cell catalyst of the present invention may contain RuTe ₂ and N element or further Fe element only as active components, and may further contain other active components made of other transition metals. .
Further, the fuel cell catalyst of the present invention may be composed only of an active component, or may be one in which an active component is adhered to a substrate.

  In the following description, a fuel cell catalyst that is substantially composed only of active components without being coated with active components is referred to as “essential catalyst”, and the active components are deposited on the substrate. The prepared fuel cell catalyst may be referred to as an “adhered catalyst”.

<Active ingredient>
The fuel cell catalyst of the present invention contains RuTe ₂ and N element, or further Fe element as active components. In addition to this RuTe ₂ and N element, or further Fe element, other components can be used. In this case, the other components include ruthenium (Ru) and / or tellurium (Te).

Examples of N element source compounds to be added to RuTe ₂ include organic compounds such as NH ₃ , amine compounds, pyridine compounds, aliphatic nitro compounds, aromatic nitro compounds, heterocyclic compounds, HNO ₃ , HNO _2, etc. However, it is not limited to these. Further, as Fe element source compounds to be added to RuTe ₂ , ferrous oxalate FeC ₂ O ₄ .2H ₂ O, ferrous chloride FeCl ₂ .nH ₂ O, anhydrous ferric chloride FeCl ₃ , ferrous sulfate Examples include, but are not limited to, iron FeSO ₄ · 7H ₂ O, ferrous sulfamate solution Fe (NH ₂ SO ₃ ) ₂ · 5H ₂ O, ferric nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, and the like. It is not something.

When the fuel cell catalyst of the present invention further contains Ru as an active component in addition to RuTe ₂ and N element, or further Fe element, the content thereof is Ru element in RuTe ₂ contained in the catalyst in terms of Ru element. Preferably it is 5 times or less with respect to an element, More preferably, it is 3 times or less, Most preferably, it is 1 time or less.
Further, when the fuel cell catalyst of the present invention further contains Te as an active component, the content thereof is preferably 10 times mol or less with respect to the Ru element of RuTe ₂ contained in the catalyst in terms of Te element. Preferably it is 5 times mol or less, Most preferably, it is 2 times mol or less.
If these abundance ratios exceed this range, the activity tends to be low.
When the fuel cell catalyst of the present invention contains RuTe ₂ and N element as an active component, or Ru and Te in addition to Fe element, these contents are contained in the catalyst in terms of total elements. It is preferable that it is 5 times mol or less with respect to Ru element in ₂ , more preferably 3 times mol or less, and most preferably 1 time mol or less.

  The abundance ratio of each element in the catalyst can be quantified by inductively coupled plasma emission spectrometry after the catalyst is weighed and then decomposed by melting with an alkali, added with an acid, and constant volume.

Incidentally, tellurium constituting the active ingredient may be a Te elements constituting the RuTe _2, TeO _2, TeO oxides such as _{3, H 2 TeO 3, H} 6 TeO 6 such oxo acids, TeCl _2, TeBr inorganic compounds such as chlorides, such as _2, and may be in the form of organic compounds such as tellurophenes. In addition, ruthenium can take a form of bonding with an organic compound in addition to an inorganic compound such as a metal element, an oxide, or a chloride. For example, ruthenium may be a Ru element constituting RuTe ₂ , an oxide such as RuO and RuO ₂ , a chloride such as RuCl ₃ .xH ₂ O, and an inorganic such as Ru (NO) (NO ₃ ) _3. It may be in the form of binding to a compound, an organic compound such as ruthenium acetylacetonate Ru (acac) ₃ and Ru ₃ (CO) ₁₂ .

N element may also take the form of heterocyclic compounds containing 6-membered rings such as oxides such as NO and NOx, aliphatic nitro compounds, aromatic nitro compounds, pyridine and triazine (hereinafter referred to as “nitrogen components”). Called.).
Fe element may also be Fe element, oxides such as FeO, Fe ₃ O ₄ , Fe ₂ O ₃ , ferrous sulfate FeSO ₄ .7H ₂ O, ferrous sulfamate solution Fe (NH ₂ SO ₃ ) It may take the form of ₂ · 5H ₂ O, ferric nitrate Fe (NO ₃ ) ₃ · 9H ₂ O (hereinafter referred to as “iron component”).

These tellurium component, ruthenium component, nitrogen component and iron component constituting the active component may be present without a bond, or may be present with a bond. In the case where these elements have a bond and the elements are directly bonded to each other, the active component may be a so-called alloy.
Further, when the RuTe ₂ component, the nitrogen component, and further the iron component have a bond, it is expected that the oxygen reduction reaction start potential is increased by the interaction.

  The existence form of the element constituting the active component in the fuel cell catalyst of the present invention can be confirmed by X-ray diffraction (XRD). That is, for example, it can be confirmed by irradiating an active ingredient deposited on a substrate described later with X-rays (Cu-Kα rays) and observing the diffraction spectrum thereof.

  Examples of the measurement apparatus and measurement conditions include the following, but the XRD analysis method for the fuel cell catalyst of the present invention is not limited to the following measurement apparatus and measurement conditions.

(Powder XRD analysis)
Measuring device X-ray powder analysis device / PANallytical PW1700
Measurement conditions X-ray output (Cu-Kα): 40 kV, 30 mA
Scanning axis: θ / 2θ
Measurement range (2θ): 3.0 ° to 90.0 °
Measurement mode: Continuous
Reading width: 0.05 °
Scanning speed: 3.0 ° / min
DS, SS, RS: 1 °, 1 °, 0.20mm

Specifically, RuTe ₂ has 21.808 °, 27.920 °, 31.287 °, 32.716 °, 43.369 ° as 2θ (± 0.3 °) peaks of X-ray diffraction. Those giving characteristic peaks such as 45.203 °, 48.322 °, 51.509 °, 53.981 °, 56.910 °, 68.565 °, 21.767 °, 26.189 °, 27 877 °, 31.249 °, 32.658 °, 33.847 °, 36.719 °, 39.822 °, 43.308 °, 44.377 °, 45.177 °, 45.801 °, 48 Those giving characteristic peaks such as 244 °, 50.117 °, 50.661 °, 51.426 °, 27.857 °, 31.271 °, 34.344 °, 39.873 °, 47. 123 °, 49.353 °, 51.532 °, 53.614 °, Characteristic peaks such as 7.636 °, 65.236 °, 67.032 °, 68.881 °, 72.414 °, 77.547 °, 80.922 °, 82.608 °, 85.948 °, etc. What you give.

<N · Fe element / RuTe ₂ weight ratio>
The weight ratio of N element / RuTe ₂ contained in the fuel cell catalyst of the present invention is usually 10 or less, preferably 3 or less, more preferably 1 or less, usually 0.01 or more, preferably 0.03 or more, more preferably. Is 0.05 or more. If the amount of RuTe ₂ is larger than this range and the amount of N element is small, the oxygen reduction reaction initiation potential is not improved. Conversely, if the amount of RuTe ₂ is smaller than this range and the amount of N element is large, the same result is obtained.
Further, when the fuel cell catalyst of the present invention further contains Fe element, the weight ratio of Fe element / RuTe ₂ contained in the fuel cell catalyst is usually 10 or less, preferably 3 or less, more preferably 1 or less. 0.01 or more, preferably 0.03 or more, more preferably 0.05 or more. If there is more RuTe ₂ than this range and less Fe element, the oxygen reduction reaction initiation potential will not be improved, and conversely, even if there is less RuTe _{2 and} more Fe element than this range, the same result will be obtained.

  When the fuel cell catalyst of the present invention contains N element and Fe element, the content ratio of N element and Fe element in the fuel cell catalyst is not particularly limited, but N element / Fe element weight ratio is It is preferably 1/100 or more, particularly 1/10 or more, and 100 or less, particularly 10 or less.

<Pure catalyst shape>
There is no particular limitation on the shape of the pure catalyst made of the active component not deposited on the substrate, but it is most generally particulate. The average particle size of the particulate pure catalyst is usually 100 μm or less, preferably 1000 nm or less, more preferably 500 nm or less, especially 300 nm or less, usually 0.5 nm or more, preferably 1.0 nm or more, more preferably 2.0 nm. That's it. If the particle size of the pure catalyst is less than this range, it becomes unstable and easily deactivates, and if it exceeds this range, it becomes difficult to obtain high activity.

  In addition, the average particle diameter of the pure catalyst is measured by unifying the direction of measuring the length of the particle diameter with a scanning electron microscope (SEM) or transmission electron microscope (TEM) and measuring the particle length in that direction. This is shown as an average value.

Specific examples of using a combination of RuTe ₂ and an N element or further an Fe element as a pure catalyst include the following i) to iii).
i) RuTe ₂ and a nitrogen component, and further an iron component are mixed together.
ii) RuTe ₂ carries a nitrogen component and further an iron component.
iii) RuTe ₂ is supported on the nitrogen component and further on the iron component.

<Substrate>
The catalyst for a fuel cell of the present invention may be a pure catalyst composed only of the above-mentioned active component, but the active component is applied to a substrate for holding and electrically conducting the active component. Is also possible. In view of obtaining high conductivity, it is preferable to use the above-mentioned active component by applying it to a substrate.

  Although there is no restriction | limiting in particular as a base | substrate used by this invention, Use of a carbon-type base | substrate is suitable at the point from which high electroconductivity is acquired.

  Various carbon-based substrates can be used and are not particularly limited. Examples thereof include carbon black, ketjen black, carbon nanotube, carbon nanohorn, carbon nanocluster, fullerene, pyrolytic carbon, and activated carbon. The carbon-based substrate may be a vapor-grown carbon fiber (Vapor Growth Carbon Fiber: hereinafter sometimes abbreviated as “VGCF”) by a vapor-phase method. It has moderate elasticity and is suitable.

Among these carbon-based substrates, carbon black is industrially advantageous in terms of conductivity, availability, and cost. Examples of carbon black include channel black, furnace black, thermal black, acetylene black, oil furnace black, and gas furnace black.
These carbon-based substrates can be used singly or in combination of two or more.

The specific surface area of the substrate is not particularly limited, but is usually 5 m ² / g or more, preferably 100 m ² / g or more, more preferably 150 m ² / g or more, and usually 5000 m ² / g or less, preferably 2000 m ² / g. The following is preferable. If the specific surface area is too small, the effective area for depositing the active ingredient is reduced, and the reaction field is reduced, so that sufficient catalytic activity cannot be obtained. When the specific surface area is excessively large, the pore diameter of the substrate may be small, and even if the active component is deposited in the small pores, sufficient catalytic activity cannot be obtained. The specific surface area of the substrate is measured by the BET method.

  The form of the substrate is not particularly limited, but the most commonly used is a powder form.

<Adhesion of active ingredient to substrate>
In the present invention, the state in which the active component is applied to the substrate refers to a state in which the active component and the substrate are in contact with each other so as to obtain electrical conductivity. Therefore, the active ingredient can be applied to the substrate by simply mixing the active component and the substrate. However, as described later, after mixing the active compound supply compound and the substrate, the mixture is calcined and coated. It is preferable to wear. Alternatively, the substrate and the active component may be mixed and then fired. In the following, the state in which the active ingredient is mixed with the active ingredient supply compound or the active ingredient and then baked to deposit the active ingredient is referred to as “supporting”.

Specific examples in which RuTe ₂ and N element or further Fe element are used in combination include the following i) to vii). Of these, those that employ “support” are particularly preferred because fine catalyst particles can be obtained.
i) RuTe ₂ and a nitrogen component, and further an iron component are mixed with the substrate.
ii) RuTe ₂ and a nitrogen component as well as an iron component are both supported on the substrate.
iii) RuTe ₂ and a nitrogen component, and further an iron component are mixed and then mixed with the substrate.
iv) RuTe ₂ is loaded with a nitrogen component and further an iron component and then mixed with the substrate.
v) RuTe ₂ is supported on the nitrogen component and further the iron component and then mixed with the substrate.
vi) RuTe ₂ is supported after the nitrogen component and further the iron component are supported on the substrate.
vii) After supporting RuTe ₂ on a substrate, a nitrogen component and further an iron component are supported.

  The shape of the active ingredient applied to the substrate is not particularly limited, but the most common is a particulate form. The average active particle size of the particulate active ingredient is usually 100 μm or less, preferably 1000 nm or less, more preferably 500 nm or less, especially 300 nm or less, usually 0.5 nm or more, preferably 1.0 nm or more, more preferably 2 It is desirable that it is 0.0 nm or more. If the particle size of the active ingredient is below this range, it becomes unstable and easily deactivated, and if it exceeds this range, it becomes difficult to obtain high activity.

  The average particle size of the active ingredient deposited on the substrate is determined by unifying the direction in which the particle length is measured with a scanning electron microscope (SEM) or transmission electron microscope (TEM). The particle length is measured and indicated as an average value.

  In order to deposit such a small average particle size active ingredient on a substrate, the production method may be devised as described later. Among these, it is preferable to control the state of crystal growth by lowering the firing temperature after mixing the substrate and the active component and shortening the firing time.

The deposition ratio of the active ingredient to the substrate is not particularly limited, but the weight ratio of Ru / (Ru + substrate) is usually 10 ⁻⁵ or more, preferably 0.001 or more, more preferably 0.8. It is preferably 01 or more, particularly 0.05 or more, and usually 0.95 or less, preferably 0.4 or less, and especially 0.3 or less. If the deposition ratio of the active ingredient is below this lower limit, the desired activity cannot be obtained, and if it exceeds the upper limit, the activity improvement effect due to deposition is less likely to occur.

<Other catalyst components>
In the present invention, a transition metal may be further deposited on the substrate as long as the effects of the present invention are not impaired.

This transition metal (hereinafter sometimes referred to as “other catalyst component”) is an element belonging to the fourth to sixth periods of groups IIIA to VIIA, VIII, and IB of the periodic table, and titanium ( Ti), vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum ( Examples include Mo), lanthanum (La), europium (Eu), gold (Au), cerium (Ce), tantalum (Ta), tungsten (W), rhenium (Re), praseodymium (Pr), and neodymium (Nd). It is preferable that the value of the standard electrode potential E ° (25 ° C.) in the aqueous solution is positive, preferably represented by the following electrochemical equilibrium type oxidant + ne ⁻ = reduced form. This is because elution due to oxidation is unlikely to occur as a natural property of metals, and there is little deterioration of the catalyst due to it. Specific examples of such materials include gold and silver.

  However, in order to make the catalyst more industrially advantageous, it is better to reduce the number of expensive catalyst components as much as possible.

  Of course, platinum (Pt) can be used in combination as a transition metal. However, since platinum is expensive, it is inexpensive and practical to add a small amount while considering the desired catalytic activity. It is desirable to provide a fuel cell catalyst. When platinum is added, specifically, the weight ratio of the total platinum component / active ingredient is usually 0.001 or more, preferably 0.01 or more, more preferably 0.05 or more, and usually 0.4 or less, preferably Is preferably 0.3 or less, and more preferably 0.2 or less.

  In addition, the following shows the electrochemical equilibrium formula of main transition metals and the standard electrode potential E ° (25 ° C.).

  These transition metals as other catalyst components may be used alone or in combination of two or more.

In the case where an active component containing RuTe ₂ and N element or further Fe element and another catalyst component are used in combination, examples of the combined form of the other catalyst component include the following.
i) RuTe ₂ and N element, or further Fe element are mixed with other catalyst components to the substrate.
ii) RuTe ₂ and N element, or further Fe element are supported on the substrate together with other catalyst components.
iii) RuTe ₂ and N element or further Fe element are mixed with other catalyst components and then mixed with the substrate.
iv) RuTe ₂ and N element or further Fe element are mixed with the substrate after supporting other catalyst components.
v) After supporting RuTe ₂ and N element or further Fe element on the substrate, other catalyst components are supported on the substrate.
vi) After supporting other catalyst components on the substrate, support RuTe ₂ and N element, or further Fe element on the substrate.

When the fuel cell catalyst of the present invention contains a transition metal as another catalyst component, the weight ratio of the total of transition metals / the total of RuTe ₂ and N elements, or further the Fe element, in the fuel cell catalyst of the present invention. Is usually 0.001 or more, preferably 0.01 or more, especially 0.05 or more, and usually 0.5 or less, preferably 0.4 or less, and particularly preferably 0.3 or less. If this weight ratio is less than this range, it is difficult to obtain the desired activity, and if it exceeds this range, it is difficult to improve the activity.

  The transition metal contained in the fuel cell catalyst of the present invention is preferably in the form of powder. The average particle size of the powder is usually 1000 nm or less, preferably 500 nm or less, and more preferably 300 nm or less, and usually 0.5 nm or more. When the average particle size is less than this range, the catalyst becomes unstable and easily deactivates, and when it exceeds this range, it is difficult to obtain high activity.

  The average particle diameter of the transition metal powder in the catalyst is determined by unifying the direction of measuring the length of the particles with a scanning electron microscope (SEM) or transmission electron microscope (TEM). The length is measured and shown as an average value.

  In the fuel cell catalyst of the present invention, a metal component other than the transition metal element may be contained in an amount of several weight percent or less based on the weight of the active component.

Catalysts containing RuTe ₂ and N elements as active components, or further Fe elements and transition metals, especially catalysts in which RuTe ₂ and N elements, or further Fe elements and transition metals are supported on a substrate, have catalytic activity. high. This is presumably because the transition metal functions as a cocatalyst for the active component and the activity is improved.

<Manufacture of pure catalyst>
There is no particular limitation on the method for synthesizing the pure catalyst of the first aspect composed only of the active component not deposited on the substrate, and any known method can be used.

  For example, an element supply compound as an active ingredient, that is, a precursor of the active ingredient is dissolved or dispersed in a solvent such as water in a predetermined molar ratio, and after filtration or evaporation of the solvent, the precursor is added as necessary. It is prepared by applying an activation step (for example, reduction treatment).

The precursor of each element is not particularly limited as long as it can be thermally decomposed. Tellurium precursors include tellurium powder (Te), halides such as TeCl ₂ , TeBr ₂ and TeCl ₄ , oxides such as TeO ₂ and TeO ₃ , and oxo acids such as H ₂ TeO ₃ and H ₆ TeO _6. Inorganic salts such as These Te precursors may be used alone or in combination of two or more.

On the other hand, examples of the ruthenium precursor include ruthenium halides, oxides, inorganic salts, organic acid salts, and the like, as well as compounds that bind to organic compounds. Specific examples of the ruthenium compound include halides such as RuCl ₃ .xH ₂ O, RuBr ₃ , Ru (SO ₄ ) ₂ , Ru (NO) (NO ₃ ) ₃ , K ₂ RuO ₄ .H ₂ O, and the like. Examples thereof include inorganic salts, organic acid salts such as Ru ₂ (OCH ₃ CO) ₄ , and organic compounds such as ruthenium acetylacetonate (Ru (acac) ₃ ). One of these ruthenium precursors may be used alone, or two or more thereof may be mixed and used.

In order to produce a RuTe ₂ pure catalyst, for example, a ruthenium precursor such as RuCl ₃ or Ru (acac) ₃ and a Te precursor such as H ₆ TeO ₆ are mixed in a desired molar ratio (RuCl ₃ , Ru (acac) ₃ etc. The molar ratio of H ₆ TeO ₆ to water is usually 0.2 or more, preferably 1 or more, usually 10 or less, preferably 4 or less) and dissolved in water at a blending ratio according to a predetermined time (usually 10 minutes or more, Preferably, after standing for 30 minutes or more, usually 50 hours or less, preferably 30 hours or less, if necessary, a predetermined temperature (usually 60 ° C or more, preferably 100 ° C or more, preferably 300 ° C or less, preferably 200 ° C or less). ) For a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), heated or refluxed, and then a precipitate is obtained by an evaporator. That. This is air-dried at room temperature, and then in an inert gas atmosphere such as nitrogen or argon for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), a predetermined temperature (usually 100 The drying treatment is carried out at a temperature of not less than 200 ° C, preferably not less than 200 ° C, usually not more than 1000 ° C, preferably not more than 800 ° C. Next, a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), a predetermined temperature (usually 100 ° C or more, preferably 200 ° C or more, more preferably 300 ° C or more). In general, an inert gas such as nitrogen or Ar may be mixed under an air stream containing hydrogen at 1000 ° C. or lower, preferably 800 ° C. or lower. The hydrogen concentration in the inert gas is not particularly limited, but 1 % Or more, preferably 10% or more, 100% or less, or 80% or less). This makes it possible to obtain pure catalyst consisting of active component containing Rute _2.

  Thereafter, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5 wt% or less, especially about 2 wt% or less), a predetermined time (usually several tens of minutes, preferably 30 minutes or more, usually Passivation treatment may be performed to form a passive film by treatment at a predetermined temperature (usually around room temperature) for 10 hours or less, particularly 5 hours or less.

<Manufacture of a deposited catalyst>
The deposition catalyst of the second embodiment is produced by depositing an active component on a substrate. Here, the active component may be applied to the substrate by, for example, a loading method in which the active component or a precursor of the active component is mixed and baked with the substrate, a mixing method in which the active component and the substrate are simply mixed, and other impregnations. It can carry out by well-known methods, such as a method, a precipitation method, and an adsorption method.

  For example, the deposited catalyst is prepared by dissolving or dispersing a precursor of each element in a solvent such as an aqueous solution in a desired molar ratio, and impregnating the substrate with the solution or immersing the substrate in the solution, followed by filtration. Alternatively, it is prepared by depositing the precursor on the substrate by distilling off the solvent and, if necessary, activating the precursor of the active ingredient (for example, reduction treatment).

In addition, the compound similar to the compound used for manufacture of a pure catalyst can be used for the precursor of an active ingredient. Of these, RuCl ₃ .xH ₂ O, Ru (acac) ₃ and Ru (NO) (NO ₃ ) ₃ are preferable as the ruthenium precursor, and H ₆ TeO ₆ is preferable as the tellurium precursor.

Next, an example of a method for producing a deposited catalyst in which RuTe ₂ and N element are deposited on a substrate as active components will be described.
First, a desired amount of an aqueous solution of an N element source compound such as nitric acid having a predetermined concentration (usually 70 to 10% by weight) is added to a substrate such as carbon black, and a predetermined time (usually 10 minutes or more, preferably 30 minutes or more). Usually 50 hours or less, preferably 30 hours or less), and if necessary, heated or refluxed at a predetermined temperature (usually 0 ° C. or higher, preferably 20 ° C. or higher, preferably 100 ° C. or lower). Next, the mixture is recovered by filtration, and then for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) under an inert gas atmosphere such as nitrogen or argon. At a temperature of 100 ° C. or higher, preferably 200 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower. Next, under an air stream containing NH ₃ gas (inert gas such as nitrogen or Ar may be mixed, and the hydrogen concentration in the inert gas is not particularly limited, but 1% or more, preferably 10% or more, 100% or less, or 80% or less), predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), predetermined temperature (usually 100 ° C or more, preferably 200 ° C) The heat treatment is usually performed at 1000 ° C. or lower, preferably 800 ° C. or lower.

On the other hand, a Ru precursor such as RuCl ₃ or Ru (acac) ₃ and a Te precursor such as H ₆ TeO ₆ are mixed at a desired molar ratio (H ₆ TeO to RuCl ₃ , Ru (acac) _3, etc.). The molar ratio of ₆ is usually 0.2 or more, preferably 1 or more, usually 10 or less, preferably 4 or less), and a predetermined amount is mixed with a substrate such as carbon black treated with an aqueous nitric acid solution as described above. After mixing, the mixture is kept for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), a predetermined temperature (usually 100 ° C or more, preferably 200 ° C or more, Preferably, the temperature is 300 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower. Under an air stream containing hydrogen (inert gas such as nitrogen or Ar may be mixed) There are no particular restrictions on the degree of 1% or more, preferably 10% or more, heated at 100 percent, or 80% or less). As a result, a deposited catalyst in which an active component containing RuTe ₂ and an N element is supported on a substrate is obtained.

  Thereafter, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5 wt% or less, especially about 2 wt% or less) for a predetermined time (usually several tens of minutes, preferably 30 minutes or more, usually 10 It is also possible to perform a passivation treatment for forming a passive film by treatment at a predetermined temperature (usually around room temperature) for a time or less, particularly 5 hours or less.

Next, an example of a method for producing a deposited catalyst in which RuTe ₂ and N element and Fe element are deposited as active components on a substrate will be described.
In a predetermined amount of water, a base such as carbon black, a predetermined amount (usually 1 to 50% by weight) of an Fe element source compound such as ferrous oxalate and a predetermined amount (usually 1 to 50) % By weight) of an N element source compound such as phenanthrolin, and a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less). Heat or reflux at a temperature (usually 0 ° C. or higher, preferably 20 ° C. or higher, preferably 100 ° C. or lower). Next, the mixture is recovered by filtration, and is subjected to a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) under an inert gas atmosphere such as nitrogen or argon, and a predetermined temperature. (Normally 100 ° C or higher, preferably 200 ° C or higher, usually 1000 ° C or lower, preferably 800 ° C or lower). Next, under an air stream containing NH ₃ gas (inert gas such as nitrogen or Ar may be mixed, and the hydrogen concentration in the inert gas is not particularly limited, but 1% or more, preferably 10% or more, 100% or less, or 80% or less), predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), predetermined temperature (usually 100 ° C or more, preferably 200 ° C) The heat treatment is usually performed at 1000 ° C. or lower, preferably 800 ° C. or lower.

On the other hand, a Ru precursor such as RuCl ₃ or Ru (acac) ₃ and a Te precursor such as H ₆ TeO ₆ are mixed at a desired molar ratio (H ₆ TeO to RuCl ₃ , Ru (acac) _3, etc.). The molar ratio of ₆ is usually 0.2 or more, preferably 1 or more, usually 10 or less, preferably 4 or less), and a predetermined amount is mixed with a substrate such as carbon black treated with the aforementioned FE element and N element source compound. Then, after physically mixing in a mortar or the like, the mixture is subjected to a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), a predetermined temperature (usually 100 ° C. or more, preferably Is 200 ° C. or higher, more preferably 300 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower), and may be mixed with an inert gas such as nitrogen or Ar under an air stream containing hydrogen. It is not particularly limited as the hydrogen concentration in the inert gas, 1% or more, preferably 10% or more, heated at 100 percent, or 80% or less). As a result, an adherent catalyst in which an active component containing RuTe ₂ and an N element and an Fe element is supported on a substrate is obtained.

  Thereafter, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5 wt% or less, especially about 2 wt% or less), a predetermined time (usually several tens of minutes, preferably 30 minutes or more, usually Passivation treatment may be performed to form a passive film by treatment at a predetermined temperature (usually around room temperature) for 10 hours or less, particularly 5 hours or less.

Further, RuTe ₂ is prepared in advance by the above-described known method, and this is mixed with a substrate subjected to N element introduction treatment such as nitric acid treatment or Fe element and N element introduction treatment, and kneaded in a mortar or the like, The active ingredient can also be applied to the substrate. This mixing may be dry or wet, but is preferably wet mixed using a medium such as water and then dried at about 100 to 200 ° C.

Among the above-described catalyst production methods, a support method in which a carbon-based substrate subjected to a desired element introduction treatment and a material selected from a precursor of a RuTe ₂ active component are mixed and then fired is preferable. This calcination can improve the activity of the resulting catalyst. The reason why the activity can be improved by firing in this way is not necessarily clear, but since the active component is deposited on the carbon-based substrate, the sintering of the active component is suppressed during firing, and the activity is reduced. Is estimated to be due to the improvement.

  When the above-mentioned transition metal is applied to the substrate together with the active component, the transition metal may be applied simultaneously in the active component application step, and the transition metal is applied before or after the active component application step. May be. Here, the “active component deposition step” includes the treatment process for depositing the active component, that is, the entire process from the addition of the active component precursor to the provision of the active component.

  As transition metal precursors for depositing transition metals on the substrate, oxides, inorganic acid salts such as nitrates, sulfates and carbonates, organic acid salts such as acetates, halides, hydrides, Examples include carbonyl compounds, amine compounds, olefin coordination compounds, phosphine coordination compounds, and phosphite coordination compounds. These may be used alone or in combination of two or more.

In order to deposit the transition metal together with the active component on the substrate, for example, a catalyst in which the active component containing RuTe ₂ and N element or further Fe element synthesized by the above-described method is supported on the substrate is chloride. A solution in which a transition metal compound is dissolved is added and allowed to stand for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), and then the solvent is distilled off by an evaporator. In this case, ultrasonic treatment may be performed. Next, under an air stream containing hydrogen (inert gas such as nitrogen or Ar may be mixed, the hydrogen concentration in the inert gas is not particularly limited, but is 1% or more, preferably 10% or more, 100 % Or less, or 80% or less) at a predetermined temperature (usually 100 ° C. or higher, preferably 150 ° C. or higher, usually 800 ° C. or lower, preferably 500 ° C. or lower) for a predetermined time (usually 10 minutes or longer, preferably 30 minutes or longer). Usually 50 hours or less, preferably 30 hours or less). As a result, an adherent catalyst in which an active component containing RuTe ₂ and N element, or further Fe element, and a transition metal are both supported on a substrate is obtained.

  Thereafter, the adsorbed catalyst is further subjected to a predetermined time (usually several tens of minutes or more, preferably 30) in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5 wt% or less, especially about 2 wt% or less). It is also possible to carry out a passivation treatment for forming a passive film by treating at a predetermined temperature (usually around room temperature) at a time of not less than minutes and usually not more than 10 hours, especially not more than 5 hours.

  As described above, the transition metal may be used as it is by mixing it with the substrate to which the active component is applied, or may be used by mixing the active component with the substrate to which the transition metal is applied.

[Fuel cell electrode material, fuel cell, fuel cell stack, fuel cell system]
The electrode material for a fuel cell and the fuel cell of the present invention contain the above-described catalyst for a fuel cell of the present invention. The fuel cell electrode material and the fuel cell of the present invention may contain only one type of the fuel cell catalyst of the present invention, or may contain two or more types.
The fuel cell stack of the present invention is characterized by using such a fuel cell of the present invention.
The fuel cell system of the present invention is characterized by using such a fuel cell stack of the present invention.

  The fuel cell according to the present invention is a power generator that supplies fuel to the anode and oxidant to the cathode, takes out the potential difference between the anode and cathode as a voltage, and supplies it to the load as described above. Consists of an electrolyte sandwiched between

  In a polymer electrolyte fuel cell, an ion exchange membrane is used as an electrolyte. Solid polymer type fuel cells include both PEFC type fuel cells using hydrogen as a fuel and direct methanol type fuel cells (DMFC, Direct Methanol Fuel Cell) using methanol and water.

  In the case of a PEFC type fuel cell in which a catalyst layer is formed on both surfaces of an ion exchange membrane as an electrolyte, and a gas diffusion layer is formed outside the catalyst layer, the anode gas diffusion layer and the cathode gas diffusion layer are integrally formed. An electrolyte membrane / electrode assembly is used. On the other hand, in the case of a DMFC type fuel cell, an electrolyte membrane / electrode assembly in which a methanol aqueous solution current collector and a cathode gas diffusion layer are integrally formed is used. In the electrolyte membrane / electrode assembly, a partition plate is disposed on the diffusion layer side, and a plurality of unit cells including the partition plate, the electrolyte membrane / electrode assembly, and the partition plate are stacked until a desired voltage is obtained according to the application. Thus, a fuel cell stack is formed. Usually, several tens to hundreds of unit cells are stacked to form a fuel cell stack.

  As the catalyst for forming the catalyst layer of the electrolyte membrane / electrode assembly, the aforementioned fuel cell catalyst of the present invention is used.

  An ion exchange membrane as an electrolyte is only required to have a cation exchange capacity, but it is practically desired to withstand an oxidation-reduction atmosphere at a temperature of about 80 to 100 ° C., which is a use temperature of a fuel cell. Alkyl sulfonic acid resins are exclusively used. Specific examples include perfluoroalkylsulfonic acid resin membranes such as Nafion (registered trademark manufactured by DuPont), Flemion (registered trademark manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark manufactured by Asahi Kasei Co., Ltd.).

  The ion exchange membrane preferably has a thickness of about 10 μm or more and several hundreds of μm or less, but it is desirable to make the thickness thinner in order to reduce the electric resistance. Taking Nafion as an example, Nafion 115 having a thickness of about 120 μm is often used. However, an electrolyte membrane having a thickness of 30 to 50 μm including a reinforcing material has begun to be developed, and these can be used similarly. .

  The diffusion layer of the PEFC type fuel cell supplies hydrogen at the anode and air at the cathode, and also has a function as a current collector for taking out the generated voltage. Therefore, the diffusion layer is preferably made of a material that is an excellent electronic conductor, allows both hydrogen and air gases to flow through, and can withstand the working atmosphere. As a material constituting the anode gas diffusion layer and the cathode gas diffusion layer, a carbon porous body such as carbon paper or carbon cloth having a thickness of usually about 100 to 500 μm, preferably about 100 to 200 μm is used. Similarly, the material of the methanol aqueous solution current collector of the DMFC type fuel cell is selected from materials in which the methanol aqueous solution circulates and can withstand the use atmosphere, and the thickness is usually 100 to 500 μm, preferably about 100 to 200 μm. A carbon porous body such as paper or carbon cloth is used.

  When an electrolyte membrane / electrode assembly is used in a fuel cell, a partition plate made of a material such as carbon, and in some cases, stainless steel, titanium, etc. is usually disposed behind the membrane to prevent hydrogen and air from mixing. In general, the partition plate is formed with grooves for the purpose of uniform and stable supply of hydrogen and air.

  Although there is no restriction | limiting in particular as a method of producing the electrolyte membrane / electrode assembly of the fuel cell of this invention, For example, the following methods are mentioned.

  Next, an example of a method for forming the cathode side catalyst layer and the anode side catalyst layer on the ion exchange membrane will be described. First, the fuel cell catalyst of the present invention described above is put in a suitable container, and a Nafion solution (concentration: 5% by weight, manufactured by Aldrich) in which Naponion (registered trademark) of DuPont is dissolved, and a medium such as alcohol, water, etc. Disperse to prepare a catalyst slurry. At this time, it is more preferable to apply ultrasonic vibration in order to promote the dispersion well. The concentration of the fuel cell catalyst of the present invention in the catalyst slurry is preferably about 1 to 50 g / L in order to obtain a desired dispersibility. Of course, a binder such as polytetrafluoroethylene (PTFE) may be added to the slurry in the range of about 3 to 30% by weight for the purpose of imparting water repellency or preventing the catalyst layer from peeling off. In addition, when the contents are to be agglomerated and made into a paste, the alcohol has 2 to 5 carbon atoms such as ethanol or isopropyl alcohol, preferably a lower alcohol having about 2 to 4 carbon atoms, or 2 to 5 carbon atoms such as ethylene glycol, preferably A polyhydric alcohol having about 2 to 4 carbon atoms can be added and aggregated so as to have a ratio of 0.25 to 1.0 with respect to water.

  The catalyst slurry thus obtained is deposited on an ion exchange membrane, a gas diffusion electrode material or a transfer film, and then dried to form a cathode side catalyst layer and an anode side catalyst layer.

Specifically, the cathode side catalyst layer and the anode side catalyst layer are respectively formed on the ion exchange membrane or the gas diffusion electrode material by any one of the following methods a) to d).
a) A catalyst slurry is sprayed on the ion exchange membrane to be used and dried.
b) A catalyst slurry is sprayed onto a gas diffusion electrode material such as carbon paper and dried.
c) A catalyst slurry is sprayed onto a transfer film material such as a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) film (development treatment) and dried, and the surface opposite to the transfer film surface is desired such as Nafion. The catalyst layer is transferred by appropriately pressing on the ion exchange membrane.
d) Similarly to c), after the catalyst slurry is spread on the FEP film, the slurry is covered with a gas diffusion electrode material such as carbon paper and dried.

In any of the cathode side catalyst layer and the anode side catalyst layer, the catalyst adhesion amount is usually 0.01 mg / cm ² or more, preferably 0.1 mg / cm ² or more, usually 50 mg / cm as the Ru adhesion amount (weight per unit area). It is cm ² or less, preferably 20 mg / cm ² or less, and most preferably about 10 mg / cm ² or less. If the amount of the active component attached is less than this range, sufficient catalytic activity cannot be obtained, and if it is more than this range, it is difficult to form an electrolyte membrane / electrode assembly.

  The catalyst layer may be formed on the ion exchange membrane and then laminated with the anode gas diffusion layer material or the cathode gas diffusion layer material. The catalyst layer may be formed on the anode gas diffusion layer material or the cathode gas diffusion layer material. May be laminated with an ion exchange membrane. The laminated body is preliminarily pressure-molded and then pressure-heat-molded with a press to obtain an electrolyte membrane / electrode assembly. In this joined body, the above-mentioned cathode-side catalyst layer is formed on one surface of the ion exchange membrane, the anode-side catalyst layer is formed on the opposite surface of the ion-exchange membrane, and the outer sides of both catalyst layers. The gas diffusion layers constituting the anode and the cathode are respectively laminated.

  In addition, when press-molding a laminated body preliminarily, it is preferable to set temperature and pressure lower than the conditions of the main molding and to set the time short as long as the collapse of the catalyst layer is prevented. This is because the catalyst particles and the gas diffusion layer porous body do not cause compression failure.

  The fuel cell system of the present invention, for example, a fuel cell system for PEFC, has a high-pressure hydrogen as a fuel gas in addition to the above fuel cell stack that obtains an electromotive force by an electrochemical reaction, a compressor that supplies compressed air as an oxygen-containing gas. A hydrogen cylinder for storing in a compressed state. In addition, a catalytic combustor that combusts exhaust hydrogen and exhaust air that have not been used for power generation in the fuel cell stack may be provided as necessary. Further, hydrogen may be supplied by a reforming reaction such as methanol, natural gas, or methane. In that case, the fuel cell system uses a tank of methanol, natural gas or methane, a water tank, a mixer of methanol and water, an evaporator for evaporating methanol aqueous solution, etc. instead of a hydrogen cylinder, a reforming reaction. A reformer to perform is provided. Furthermore, in order to prevent poisoning of the fuel cell by carbon monoxide contained in the hydrogen gas after the reforming reaction, a carbon monoxide reduction device may be provided.

  In addition, the fuel cell system for DMFC of the present invention includes a fuel cell stack that obtains an electromotive force by an electrochemical reaction, a compressor that supplies compressed air as an oxygen-containing gas, and a methanol aqueous solution container that is fuel. The aqueous methanol solution is sent to the anode electrode of the fuel cell stack by a feed pump. The aqueous methanol solution may be supplied to the anode electrode after being heated and vaporized by an evaporator in advance. In addition, an aqueous methanol solution not used for power generation in the fuel cell stack may be collected and returned to the aqueous methanol solution container. The methanol aqueous solution may be collected using a gas-liquid separator when necessary.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited by a following example.

[Powder XRD analysis]
In the following examples and comparative examples, XRD analysis of the prepared catalysts was performed under the following conditions.
Measuring device X-ray powder analysis device / PANallytical PW1700
Measurement conditions X-ray output (Cu-Kα): 40 kV, 30 mA
Scanning axis: θ / 2θ
Measurement range (2θ): 3.0 ° to 90.0 °
Measurement mode: Continuous
Reading width: 0.05 °
Scanning speed: 3.0 ° / min
DS, SS, RS: 1 °, 1 °, 0.20mm

[Measurement of oxygen reduction reaction initiation potential]
In the following examples and comparative examples, the oxygen reduction reaction initiation potential (onset potential) was defined as the potential at which a current exceeding 5 A / 1 g-Ru was obtained in the produced cathode electrode.
The measurement conditions for the oxygen reduction starting potential are as follows.
Electrolyte: 0.5 MH ₂ SO ₄ aqueous solution
Atmosphere: 1 atmosphere oxygen atmosphere Scanning speed: 5 mV / sec
Scanning range: 50 to 850 mV
Working electrode: rotating disk, glassy carbon disk 4φ
Counter electrode: Pt mesh electrode Comparative electrode: Standard hydrogen electrode (SHE)
Rotation speed: 1600rpm

When the electrode potential is scanned from about 850 mV to a low potential (50 mV) with respect to the standard hydrogen electrode, 4H ⁺ + O ₂ + 4e ⁻ → 2H ₂ O between the working electrode and the Pt counter electrode
It can be seen that the oxygen reduction current due to. After reaching 50 mV, the current value that flows when scanning in the direction of high potential (850 mV) is converted into a current value per unit weight (1 g) of Ru contained in the manufactured cathode electrode, and 5 A / 1 g-Ru. The potential exceeding the value was defined as the oxygen reduction reaction start potential.
At that time, as a blank test, the atmosphere was nitrogen, the rotation speed was 0 rpm, the current value flowing under the same scanning conditions (scanning speed: 5 mV / second, scanning range: 50 to 850 mV) was measured, and this value was used as the previous oxygen. The value obtained by subtracting from the current value at 1 atm was taken as the oxygen reduction current value by the produced cathode electrode catalyst.

[Example 1]
<Preparation of RuTe ₂ / N coated catalyst>
Carbon black (VULCAN XC-72R (manufactured by Cabot, specific surface area (BET) 254 m ² / g) was added with 300 ml of 30% by weight nitric acid and treated at reflux temperature for 3 hours. And dried for 2 hours at 200 C under an argon stream, and then transferred to a calcining tube and treated for 3 hours at 600 ° C. under an NH ₃ stream of 10 ml / min, then Ru (acac) ₃ 0.394 g, H _6. TeO _{6 (} 0.454 g) and carbon black (0.4 g) subjected to the N element introduction treatment were physically mixed in a mortar, and the mixture was placed in a firing tube and heated from room temperature to 300 ° C. in 25 minutes under a hydrogen gas stream. After heating, the temperature was raised from 300 to 500 ° C. over 3 hours, and then allowed to stand at 500 ° C. for 2 hours. In O ₂ -98% _{N 2} atmosphere and passivated was removed catalyst.

This catalyst was analyzed by XRD analysis according to RuTe ₂ (value of 2θ, 21.925 °, 26.232 °, 27.925 °, 31.418 °, 32.726 °, 34.026 °, 36.525 °, 39.828 °, 43.456 °, 45.564 °, 46.933 °, 48.666 °, 51.571 °, 53.734 °, 57.225 °, 59.781 °, 65.371 °, 66.848 °, 68.474 °, 73.070 °, 78.389 °, 80.970 °, 82.277 °, and 85.874 °).

<Creation of cathode electrode>
20 mg of the obtained RuTe ₂ / N-deposited catalyst was suspended in 20 mL of water, sufficiently stirred with an ultrasonic cleaner, and then the amount of Ru deposited with a microsyringe (calculated assuming that Ru and Te elements were not volatilized. The same applies to the examples and comparative examples of Example 1 and Example ² ) and dropped onto a glassy carbon electrode as a working electrode so as to be 15 μg / cm ² . 10 μL of a liquid diluted 100 times by weight with water was added dropwise and allowed to dry to form a cathode electrode.
With respect to this cathode electrode, the obtained oxygen reduction reaction initiation potential and activity at a predetermined potential were examined, and the results are shown in Table 2.

[Example 2]
<Preparation of RuTe ₂ / N · Fe coated catalyst>
Carbon black (VULCAN XC-72R (manufactured by Cabot, specific surface area (BET) 254 m ^{2 /} g) 0.4 g, ferrous oxalate 0.0129 g and phenanthrolin 0.0426 g were added with 50 ml of water, and the reflux temperature was increased. The carbon black was collected by filtration and dried under an argon stream at 300 ° C. for 2 hours, then transferred to a calcining tube and treated at 800 ° C. for 2 hours under an NH ₃ stream of 10 ml / min. Next, 0.394 g of Ru (acac) _3, 0.454 g of H ₆ TeO ₆ and 0.4 g of carbon black subjected to the N element and Fe element introduction treatment were thoroughly physically mixed in a mortar. It was put in a tube, heated from room temperature to 300 ° C. in 30 minutes under a hydrogen gas stream, and then heated from 300 to 500 ° C. in 3 hours. After 2 hours standing was. After the reaction at 500 ° C., after cooling to room _temperature, taken out of the catalyst was passivated with 2% O 2 -98% _{N 2} atmosphere.

This catalyst was analyzed by XRD analysis according to RuTe ₂ (value of 2θ, 21.820 °, 26.183 °, 27.928 °, 31.322 °, 32.682 °, 34.028 °, 39.966 °, 43.426 °, 45.370 °, 47.220 °, 48.377 °, 51.482 °, 53.775 °, 57.021 °, 58.967 °, 59.817 °, 65.278 °, 66.986 °, 68.522 °, 71.523 °, 78.172 °, 78.326 °, 80.925 °, 82.434 °, and 86.073 °). It was confirmed.

<Creation of cathode electrode>
Except for using the obtained RuTe ₂ / N · Fe deposited catalyst, a cathode electrode was prepared by the same method as in Example 1 so that the amount of Ru deposited was 15 μg / cm ² and evaluated in the same manner. The results are shown in Table 2.

[Comparative Example 1]
<Preparation of RuTe ₂ coated catalyst>
Ru (acac) ₃ 0.788 g, H ₂ TeO ₆ 0.909 g and carbon black (VULCAN XC-72R (manufactured by Cabot, specific surface area (BET) 254 m ^{2 /} g)) were physically mixed in a mortar. This mixture was placed in a firing tube, heated from room temperature to 300 ° C. in 25 minutes under a hydrogen gas stream, then heated from 300 to 500 ° C. over 3 hours, and then allowed to stand at 500 ° C. for 2 hours. After completion, the mixture was cooled to room temperature and then passivated in a 2% O ₂ -98% N ₂ atmosphere to take out the catalyst.

This catalyst was analyzed by XRD analysis with RuTe ₂ (value of 2θ, 21.507 °, 27.805 °, 31.300 °, 32.743 °, 40.041 °, 43.498 °, 45.356 °, 48 .246 °, 51.441 °, 54.002 °, 57.057 °, 59.850 °, 65.395 °, 68.306 °, 73.347 °, 82.394 °, 85.753 °, 86 , Which gave a peak at 095 °).

<Creation of cathode electrode>
Except for using the obtained RuTe ₂ deposition catalyst, a cathode electrode was prepared by the same method as in Example 1 so that the amount of Ru deposited was 15 μg / cm ² , evaluated in the same manner, and the results were shown. It was shown in 2.

  As is clear from Table 2, the catalyst using carbon black subjected to the N element or N element and Fe element introduction treatment of Example 1 and Example 2 is Comparative Example 1 using untreated carbon black. From this catalyst, the oxygen reduction reaction starting potential is increased, and the activities at 0.50 V and 0.65 V are also improved.

The deposited catalysts of Examples 1 and 2 and Comparative Example 1 were those in which 20% by weight of RuTe ₂ was supported on carbon black.

  According to the present invention, a practical fuel cell is provided by an inexpensive fuel cell catalyst having an increased oxygen reduction reaction start potential. Therefore, the fuel cell can be used for a fuel vehicle, a fixed cogeneration system, and the like. Expansion and practical application are promoted.

Claims (8)

A catalyst for a fuel cell comprising RuTe ₂ as an active component, wherein the active component is deposited on a carbon-based substrate heat-treated with a compound containing an N element. 2. The fuel cell catalyst according to claim 1, wherein the carbon-based substrate is further heat-treated with a compound containing Fe element. A fuel cell electrode material comprising: an ion exchange membrane; and a fuel cell catalyst layer according to claim 1 or 2 formed on the ion exchange membrane. A fuel cell electrode material comprising: an electrode gas diffusion layer; and a fuel cell catalyst layer according to claim 1 or 2 formed on the electrode gas diffusion layer. A fuel cell electrode material comprising: a transfer film; and a fuel cell catalyst layer according to claim 1 or 2 formed on the transfer film. Fuel cell characterized by using a catalyst for a fuel cell according to claim 1 or 2. A fuel cell stack using the fuel cell according to claim 6 . A fuel cell system using the fuel cell stack according to claim 7 .